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Overwintered Nucs: Learning on the Go

This article first appeared in the February 2023 First Quarter Newsletter: Part 2 of the Michigan Beekeepers Association

A few years ago, we realized that learning to overwinter nucleus colonies (nucs) was something we needed to master; both to help replace winter losses and to support the needs of local beekeepers who wanted to purchase local overwintered nucs instead of nucs or bees from the south. But how to do this?

After listening to a presentation by Mike Palmer of Vermont, I purchased two dozen nuc boxes that were two 4-frame nucs within a 10-frame box. On top of these we put a 4-frame box, allowing you to expand each colony to 3 or 4 boxes high. In the winter, the bees build their cluster against the common wall of the box, essentially creating one larger cluster that spans two colonies. These colonies are easy to work. Finding the queen is much easier in a 12- or 16-frame hive than the larger 20- or 30-frame colonies of our production hives. Our first winter, we had 12 nucs in 6 of what I call double-nuc boxes. Only half made it through. They just weren’t large enough going into winter.

I spent a lot of time reading about various ways to create mating nucs and how long the queen should be left to lay before being pulled from the hive. Many commercial breeders only leave the queen in the mating nuc long enough to confirm that she has been mated and is laying. Others talked about the advantage of letting the queen lay for a full 34 weeks before removing her. There is some data to suggest that this allows her to develop more fully and, in the end, develop into a better queen—an important factor for us, if we were going to get our nucs strong enough to survive the winter. Based on this, we decided to mate our queens in the 4-frame nucs on full-size frames. This provides lots of room for the colony to grow and for the queen to lay without needing to disturb the nuc.

The other big question was how the double-nuc configuration affected their ability to get through our Michigan winters. After reading several articles about insulation, and how the thermal dynamics of our hives compare to trees, I decided to run a test. I fully insulated 7 double nucs last winter and removed the upper entrance, something I was taught I should never do. The rest were wrapped in tar paper with an upper entrance, similar to how we treat our production hives. For all our hives, we add a spacer on top that allows us to add sugar bricks as a safety for winter feeding.

Interestingly, we didn’t see a lot of difference in survival based on insulation. It was more driven by having enough healthy bees to create a strong cluster. What we did see, however, was that come early April the insulated nucs had 50% more bees and brood than the uninsulated nucs. Was this repeatable? Hopefully yes, as last year we purchased 50 polystyrene nucs with 6-frame over 6-frame configurations. Not quite the same as 4 over 4 over 4, but similar. We also noticed that the poly nucs built up much faster over the summer. Was this because there was less temperature stress during our warmer summer months? We need another summer to validate these results and make sure this wasn’t a fluke.

The other obstacle we’re managing is how to have enough brood to support raising 50 to 100 queens using full-frame nucs. That’s 100 to 200 frames of brood if we start with a strong nuc for a new queen. I also believe that we need to raise the queens when they naturally would be raised by a colony—swarm season. If we can complete all grafting by mid-June, this is prime swarm season and should allow lots of time for the nuc to build up to a strong 12-frame nuc for winter. However, we only have 30 days to raise that 100 to 200 frames of brood. How to do that?

What we’ve decided is to use the 4-frame nucs. We call them our brood factory—thanks for the name Mike Palmer! They overwinter each year, and come mid-May we start pulling brood to support queen rearing. We often pull 1 to 2 frames of brood from each nuc each week, providing the brood frames needed for our mating nucs. Once we’re done grafting, we let these colonies build back up; sometimes collecting honey, but always being very strong and ready for winter.

This year, we plan on having 30 colonies for raising brood. We’ll graft from 3 of our best queens and, if all goes to plan, raise over 100 queens. Most will be used to create overwintered nucs, some for fall splits of our production colonies, and the balance to make sure that we have strong queens in our brood factories going into winter. As they say, let’s see how this year really goes….

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